This may be a great plugin, I can't say for sure since I've just installed it and have not yet been able to determine its effectiveness.
However I have a few comments. The installation instructions have a couple typos, particularly the tag that you need to insert in a page to create a contact form... the tag given is missing the <!-- exclamation point.
There are also no configuration options for what the required fields should be. The author of the plugin has made "website" a required field. Bah! Lots of people who might read your blog and want to comment don't have websites. This should NOT be a required field and there is no easy way to disable it that I am aware of.